/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package at.irian.demo.jsfatwork.repository.jpa;

import at.irian.demo.jsfatwork.domain.AbstractDomainObject;
import at.irian.demo.jsfatwork.repository.GenericRepository;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import java.util.List;

/**
 * Abstract repository class which provides default implementations for common repository methods.
 *
 * @author Gerhard Petracek
 */
public abstract class AbstractGenericJpaRepository<T extends AbstractDomainObject> implements GenericRepository<T>
{
    protected Class<? extends AbstractDomainObject> entityClass;

    @PersistenceContext
    protected EntityManager entityManager;

    public AbstractGenericJpaRepository()
    {
        this.entityClass = getEntityClass();
    }

    protected abstract Class<? extends AbstractDomainObject> getEntityClass();

    public void save(T entity)
    {
        if(entity.isTransient())
        {
            this.entityManager.persist(entity);
        }
        else
        {
             this.entityManager.merge(entity);  
        }
    }

    public void remove(T entity)
    {
        if (entity.isTransient())
        {
            throw new IllegalStateException("entity is not persistent");
        }

        if (this.entityManager.contains(entity))
        {
            this.entityManager.remove(entity);
        }
        else
        {
            this.entityManager.remove(loadById(entity.getId()));
        }
    }

    public List<T> loadAll()
    {
        return (List<T>) this.entityManager.createQuery("select entity from " + this.entityClass.getSimpleName() + " entity")
                .getResultList();
    }

    public T loadById(Long id)
    {
        return (T) this.entityManager.find(this.entityClass, id);
    }
}